The invention relates to a method of compacting powder comprising interweldable particles into a unitary structure.
There are various methods of exerting pressure on powder in order to compact into a unitary structure or substantially solid body (hereinafter referred to simply as a "solid body"). The best known method of compacting powder consists in pressing the powder in a form die in a crank or hydraulic press. The compacted powder, a so-called green compact, is then sintered at a high temperature (e.g. for iron powder at a temperature of about 1150.degree. C.) in a furnace with controlled temperature for about 30 minutes. After sintering, the brittleness of the compacted part largely disappears and the compact may have an acceptable strength, which approaches that of the basic metal. Such a method is, however, normally restricted to small parts. Furthermore, heavy-duty presses are required if high densities are to be reached.
Another known method of compacting metal or non-metal powder is the explosive compaction method. Normally the powder is encapsulated in a can around which an explosive is placed. Some experiments have also been made in which a body was launched by explosion of the explosive to impact on the powder, whereby the speed of the body varied about 200 m/sec. By this technique it is possible to produce compacts having a density of 92 to 98% of that of the solid body. The main advantage of this technique is that without large capital expenditure rods of high density can be produced, which, according to need, may have large dimensions.
The mechanism of compaction by explosion is, however, not yet well-known. In any case, the method of compacting powder by using explosives is not easy, is not at all controllable and it is dangerous for the operator. This method allows practically only cylinders to be produced.
It is the object of the present invention to do away with the drawbacks of the known methods of compacting powder and to provide a method of compacting powder comprising interweldable particles whereby pure materials, alloys or layered structures can be obtained, the densities of which are close to the 100% limit, i.e. they approach the density of the basic metal or other material, without the necessity of a subsequent sintering process.
It is a further object of the present invention to provide a method of compacting powder, in which pure materials, alloys or layered structures are obtained having superior qualities than those of the pure materials, alloys or layered structures produced with the usual methods of compacting powder with subsequent sintering of the compacted parts. Furthermore, in the present invention, alloys or mixtures of materials should be produced, which otherwise cannot be produced with a known method in which high temperatures are used (i.e. sintering).
A still further object of the invention is to provide a method of compacting powder, in which parts of relatively large size and of various shapes (hence not only of cylindrical shape) can be produced.